Molecular carbon skeleton with self−regulating ion−transport channels for long−life potassium ion batteries

Abstract

Developing anode materials with multiple-dimensional ion transport channels, especially to overcome huge volume expansion and sluggish ion diffusion kinetics caused by large radius of potassium ion (K+), is critical to improve the potassium storage performance. Herein, we propose a self-reversible conversion of chemical bonds with different bond lengths based on graphdiyne (GDY) to self-regulating the ion transport channels. Density functional theory (DFT) calculations and ex/in situ electrochemical tests proof the in−plane triangular−like pores (5.46 Å) of the GDY framework offer a transport channel for K+ (1.38 Å) diffusion in the direction perpendicular to the GDY plane, which differs it from carbonaceous materials whose ion diffusion is mostly governed by in−plane migration. Furthermore, the reversible alkyne−alkene bonds linking/breaking of GDY stimulated by K+ to realize self-regulating ion channels are demonstrated by in situ Raman and electro−kinetic analysis. Moreover, compared to graphite, the GDY anode with 2 orders of magnitude diffusion coefficient delivered a high reversible capacity of 202 mAh g−1 at 100 mA g−1 exhibited extraordinary durability corresponding to cycle time over 380 days. This work opens a new avenue of designing intelligent, efficient ion transport channels from molecular carbon skeleton perspective to enhance diffusion kinetic for high-performance KIBs.